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  2. Migmatite - Wikipedia

    en.wikipedia.org/wiki/Migmatite

    Migmatite is a composite rock found in medium and high-grade metamorphic environments, commonly within Precambrian cratonic blocks. It consists of two or more constituents often layered repetitively: one layer is an older metamorphic rock that was reconstituted subsequently by partial melting ("paleosome"), while the alternate layer has a ...

  3. Tonalite–trondhjemite–granodiorite - Wikipedia

    en.wikipedia.org/wiki/Tonalite–trondhjemite...

    The mafic minerals in the TTG rock body, possibly biotite, were weathered, which introduced a brownish coating on the TTG rock surface. Tonalite–trondhjemite–granodiorite ( TTG ) rocks are intrusive rocks with typical granitic composition ( quartz and feldspar ) but containing only a small portion of potassium feldspar .

  4. Metamorphism - Wikipedia

    en.wikipedia.org/wiki/Metamorphism

    Abbreviations of minerals: act = actinolite; chl = chlorite; ep = epidote; gt = garnet; hbl = hornblende; plag = plagioclase. Two minerals represented in the figure do not participate in the reaction, they can be quartz and K-feldspar. This reaction takes place in nature when a mafic rock goes from amphibolite facies to greenschist facies.

  5. Pelite - Wikipedia

    en.wikipedia.org/wiki/Pelite

    [4] [5] [6] A semipelite is defined in part as having similar chemical composition but being of a crystalloblastic nature. [7] Pettijohn (1975) [8] gives the following descriptive terms based on grain size, avoiding the use of terms such as clay or argillaceous which carry an implication of chemical composition. The Ancient Greek terms are more ...

  6. Geology of Nigeria - Wikipedia

    en.wikipedia.org/wiki/Geology_of_Nigeria

    The Migmatite-Gneiss Complex covers half of Nigeria's surface area and encompasses Archean gray gneisses, with tonalite and granodiorite consistencies. Within this complex are occurrences of schist , migmatite , garnet , sillimanite , kyanite and staurolite , which together indicate high-grade metamorphism up to the level of amphibolite on the ...

  7. Anatexis - Wikipedia

    en.wikipedia.org/wiki/Anatexis

    Anatexis (via Latin from Greek roots meaning "to melt down") is the partial melting of rocks. [1] Traditionally, anatexis is used specifically to discuss the partial melting of crustal rocks, while the generic term "partial melting" refers to the partial melting of all rocks, in both the crust and mantle.

  8. Ultra-high-temperature metamorphism - Wikipedia

    en.wikipedia.org/wiki/Ultra-high-temperature...

    Metamorphism of crustal rocks in which peak temperature exceeds 900 °C, recognized either by robust thermobarometry or by the presence of a diagnostic mineral assemblage in an appropriate bulk composition and oxidation state, such as assemblages with orthopyroxene + sillimanite + quartz, sapphirine + quartz or spinel + quartz, generally at pressure conditions of sillimanite stability in ...

  9. List of minerals - Wikipedia

    en.wikipedia.org/wiki/List_of_minerals

    This is a list of minerals which have Wikipedia articles. Minerals are distinguished by various chemical and physical properties.